1. Field of the Invention
The present invention relates to a robot for transporting semiconductor wafers, and more particularly, to a robot for transporting a plurality of processed wafers to a downstream processing station in a batch-type semiconductor fabrication facility. The present invention also relates to a method of transporting the wafers from one processing station to another.
2. Description of the Related Art
Generally, semiconductor devices are produced in a processing facility by repeatedly performing a plurality of various processes thereon. The processing facility includes transportation apparatus to transport the wafers from one processing station to another. The transportation apparatus are classified according to how they transport wafers, that is, a single-type for transporting wafers one-by-one, or a batch-type for transporting a plurality of wafers at a time.
Robots are widely used for transporting wafers between processes because they are easily controlled automatically. For example, wafer cleaning is performed by sequentially placing a plurality of wafers in a bath for etching and a bath for rinsing, repeatedly performing these steps, and then drying them. A robot is used for transporting the wafers from the etching bath to the rinsing bath and to the dryer.
FIG. 1 shows one example of a conventional robot 1 which comprises a vertical bar 2 and a horizontal bar 3. The horizontal bar 3 has a chuck 4 for holding a plurality of wafers W. The vertical bar 2 is driven by a driving part 5 which moves in both a vertical direction, causing the chuck 4 to move up and down, and back and forth longitudinally along a processing line 6 to thereby transport a plurality of wafers received in the chuck 4 to the next bath or subsequent processing station.
However, when the wafers are transported from one processing station to another by the conventional robot, they are exposed to the surrounding air. Water adhered to the wafer surface as the result of etching and rinsing processes contacts the air. As a result, marks are formed on the wafer surface which in turn result in processing defects causing a reduction in wafer quality. Therefore, in order to keep the generation of the marks to a minimum, the robot should move over as small a distance as possible.
However, especially when wafers are transported from rinsing processing equipment to a dryer, they are exposed to the air for a greater amount of time which generates marks that are substantial enough to cause severe processing defects. It is thus important to pay special attention to the transportation of the wafers during this processing step.
However, it is difficult to properly manage these processing defects caused by environmental factors. In fact, the contact of the transported wet wafers with the air creates processing defects so often that it becomes one of the main causes of low production yields.